The invention relates to a capped electric lamp provided with:
a light-transmitting lamp vessel which is closed in a gastight manner, which has an axis, and in which an electric element is arranged having a center and connected to current conductors which issue from the lamp vessel to the exterior;
a lamp cap connected to the lamp vessel, which lamp cap comprises a housing;
said housing being provided with:
contact members which are connected to the current conductors;
at least a reference means;
at least a locking means for locking the connection between the lamp vessel and the lamp cap; and
at least a coupling means.
Such a capped electric lamp is known from EP-A-0 618 609. The known lamp is provided with a pressure body to which the lamp vessel is coupled. The pressure body is coupled to the housing by means of a snap connection, said housing having a circumferential wall extending parallel to the axis. A separate elastic body, for example a rubber disc or ring, is accommodated between the pressure body and the housing, as seen in axial direction. A permanent force obtains between the housing and the pressure body owing to the elasticity of the disc or ring, so that the pressure body with the lamp vessel connected thereto remains correctly positioned with respect to the housing. A number of functional units of the lamp cap such as contact members, reference means, and coupling means, are present axially displaced relative to one another. This means that the lamp has a comparatively great constructional height in axial direction.
The known lamp is suitable for being mounted in a reflector. The lamp has a projecting collar which is provided with studs which co-operate with the reflector and by means of which the lamp cap and the reflector are coupled to one another in a rotary movement. The known lamp is highly suitable for use as a vehicle headlamp.
Car set makers require that the actions to be performed in the assembly of car components, for example lighting units for vehicles, are as simple as possible. A further wish is that the car components should be universally applicable and uniform, i.e. independent of the assembling method, such as in the case of lamps, for example, the plate, front, and back mounting methods. The known lamp should accordingly be designed for any mounting method as desired, bulb forward (back/plate mounting) or lamp cap forward (front mounting) against a support. The lamp is then held by additional means on the support, such that the electric element occupies a predetermined position with respect to this support.
A disadvantage of the known capped lamp is that it is not universally applicable owing to the comparatively large and highly asymmetrical lamp cap, for example that it is unsuitable for front mounting. A second disadvantage is the cumbersome assembly of the lamp and the lighting unit, on the one hand owing to the comparatively large number of loose components and on the other hand on account of the comparatively complicated rotary movements necessary for coupling the lamp cap to the reflector. A third disadvantage is that tolerances in the dimensions of the housing and the pressure body are compensated for by the elastic ring to a limited degree only. This means that there is a considerable risk that the housing and the pressure body bear upon one another without a permanent spring pressure, so that the housing and the pressure body can become displaced relative to one another, with the result that the electric element will no longer be correctly aligned with respect to the support.
A capped electric lamp is known from DE-B-1 034 268 where the glass bulb of the lamp is closed off by a plate of insulating material, which plate lies in a plane which is at least substantially perpendicular to the axis. A hollow cylindrical lamp cap is fixed at the side of the plate facing away from the bulb in a manner not described in any detail. The known bulb, however, is only designed for back and plate mounting. It is desirable for various applications, however, to have a lamp available which can be placed against a support with its lamp cap forward.
It is an object of the invention to provide a capped electric lamp of the kind described in the opening paragraph which is of a simple, easily manufactured construction and which counteracts the above disadvantages.
According to the invention, this object is achieved in that the coupling means forms an integral whole with the housing in that they share an integral, resilient intermediate portion. Since the lamp cap does not comprise loose components but is made from one piece, it has the advantage of a simple lamp assembly and at the same time renders possible a more compact lamp with smaller constructional dimensions. In the mounted state, the resilient intermediate portion is in a non-relaxed state, so that there is a permanent spring pressure between the coupling means and the reference means. The reference means and the coupling means thus remain in a fixed position relative to one another in the mounted state. The lamp is universally applicable because the compact lamp cap is comparatively small compared with the lamp vessel. A difference in stiffness of the resilient action of the resilient intermediate portion can be realized in a simple manner by means of thickness variations and the choice of material for the resilient intermediate portion. It is thus easy to realize a desired value of the permanent resilient force exerted between the lamp cap and a support coupled thereto, for example a reflector or an adapter, via the reference means, which is formed, for example, by studs or surfaces. It was found that a force equal to twice the force of gravity is sufficient for keeping the lamp positioned under normal practical conditions involving shock and impact loads.
In an embodiment, the lamp is characterized in that the resilient intermediate portion is displaceable around the housing in a substantially axial direction. The axial displaceability of the resilient intermediate portion around the housing may be achieved, for example, in that the resilient intermediate portion is provided with an internal dimension which, seen in one and the same plane, is greater than an external diameter of the housing. It is advantageously achieved thereby that the shape of the lamp cap is self-releasing from its mold. The mold can accordingly be free from moving parts, and the lamp cap can accordingly be manufactured in a comparatively simple and inexpensive manner.
The problem referred to as xe2x80x9cblack gapxe2x80x9d, known to those skilled in the art, may arise when the capped lamp is used as a vehicle lamp in a lighting unit. The black gap is visible as a dark ring around the luminous lamp vessel during operation of the lighting unit, which ring is surrounded by the light reflected by the reflector and originating from the electric element. The black gap is caused by light losses which occur when light originating from the electric element is incident on the lamp cap. The favorable situation in which the guidelines for counteracting the black gap problem in lighting units of vehicles are complied with is obtained in an embodiment which is characterized in that the lamp cap falls at least substantially completely within a cone having an apex in the center of the electric element and a half apex angle of at most 25xc2x0.
In a further preferred embodiment, the housing comprises a flat base portion which is at least substantially perpendicular to the axis. This base portion serves as an abutment for the placement of the lamp vessel in the lamp cap. The lamp vessel is closed in a gastight manner by means of a plate of insulating material which lies in a plane which is at least substantially perpendicular to the axis. In the manufacture of the lamp according to the invention, the electric element is mounted in a predetermined position relative to the plate of insulating material. The plate of the lamp vessel bears on the base portion of the lamp cap with a permanent compression force in the state in which the lamp vessel and the lamp cap are assembled together. The electric element thus occupies a predetermined position with respect to the reference location on the lamp cap. This embodiment of the lamp has a comparatively very small axial dimension. The housing in which the lamp is to be accommodated can be comparatively very flat thanks to this comparatively very small axial dimension.
A particularly favorable embodiment relates to a lamp wherein the lamp cap is provided with at least one decoupling means. The decoupling means is resiliently connected to the housing and together with the housing forms an at least substantially axial cylinder which surrounds the coupling means, which is preferably a resilient tag. This has the advantage that the lamp can be removed from its mounted state in a simple manner. The coupling means is in a hooked position in the mounted state. Pressing the decoupling means so far in the direction of the axis that it achieves a movement of the coupling means in the direction of the axis achieves that the coupling means leaves the hooked position, and the lamp is uncoupled and can be removed.
A further, particularly favorable embodiment relates to a lamp wherein the decoupling means is provided with a pressure stud. The relevant pressure stud has a comparatively small tangential dimension compared with a tangential dimension of a slot in hooking means of a support coupled to the lamp. This means that the pressure stud has comparatively much space, and the chance that the pressure stud will hook itself behind the hooking means while being pushed in the direction of the axis and during the removal of the lamp is comparatively small. Uncoupling of the lamp is facilitated thereby.
It is favorable to provide the lamp cap with pressure surfaces, preferably on the resilient intermediate portion, for further facilitating the handling of the lamp and bringing it into the mounted position. The contact members may be provided with screening means for avoiding direct contact between the contact members and the skin during handling of the capped lamp and/or for preventing pollution and/or damage by other causes. A more reliable operation of the contact is obtained thereby, for example in that the chance of contamination of the contact members, for example owing to inadvertent touching, is reduced.
In a further embodiment, the lamp cap is provided with an adapter. Various features may be provided on the adapter, for example standard contact points for electrical connection, whereby the assembly is further simplified, and/or, for example, a rubber ring. When the capped lamp and the adapter coupled thereto are coupled to a reflector, the adapter and the reflector will slide one over the other with narrow fit, with the ring in between, which is slightly compressed as a result and will close off the narrow passage in a gastight manner. It is counteracted thereby that volatile substances can enter the reflector through an opening between the lamp cap and the reflector. The ring is kept in position in this case, for example, in that it is present in a groove.
In another embodiment, the rubber ring is provided on the lamp cap, for example laid in a groove, so that a separate adapter is not necessary for closing off the narrow passage between the reflector and the lamp cap in a gastight manner. The penetration of volatile substances into the reflector through the narrow fit is thus counteracted in a comparatively simple manner. Alternatively, the reflector may be provided with the rubber ring instead of the lamp cap.
It is favorable when the lamp cap is constructed from synthetic resin at least for the major part. The resilient intermediate portion and the housing may then be made from the same material. It is possible in that case to give the lamp cap comparatively small dimensions because it itself is electrically insulating, which promotes safety. A wide variety of synthetic resins may be used in the lamp cap, for example thermoplastic synthetic resins, for example such materials filled with powder or with fibers, such as glass powder or glass fibers, for example polyether imide, polyether sulfon, polyether sulphide, polyphenylene sulphide, polybutylene terefthalate, etc., the latter synthetic resin being particularly suitable as a material for the housing of the lamp cap.
A further favorable embodiment is one in which the capped lamp is provided with a reflector, whereby the generated light can be focused and efficiently utilized. The use of the coupling means and the reference means of the lamp cap which cooperate with the reflector enable the reflector and the lamp cap, and accordingly the electric element, to be accurately positioned relative to one another.
The electric element of the electric lamp according to the invention may be, for example, an incandescent body, possibly in an inert gas comprising halogen. Alternatively, the element may be a pair of electrodes in an ionizable gas. In general, it will be favorable to position the electric element axially, in particular coaxially with the bulb.
The lamp cap of the electric lamp according to the invention has a universal construction which is suitable for front, back, and/or plate mounting in dependence on the support, for example adapter or plate, on which the lamp is mounted. The resilient intermediate portion and/or the housing of the lamp cap may be hollow, so that a saving can be made in lamp cap material and the lamp cap is lighter.
The electric lamp according to the invention is particularly suitable not only as a headlamp but also, for example, as a lamp at the rear of a vehicle, for example as a stop lamp, indicator lamp, tail light lamp, reversing lamp, fog rear lamp, etc.